Electronic article surveillance (“EAS”) systems are commonly used in retail stores and other settings to prevent the unauthorized removal of goods from a protected area. Typically, a detection system is configured at an exit from the protected area, which comprises one or more transmitters and antennas (“pedestals”) capable of generating an electromagnetic field across the exit, known as the “interrogation zone”. Articles to be protected are tagged with an EAS marker that, when active, generates an electromagnetic response signal when passed through this interrogation zone. An antenna and receiver in the same or another “pedestal” detects this response signal and generates an alarm.
Because of the nature of this process, other magnetic materials or metal, such as metal shopping carts, in proximity to the EAS marker or the transmitter may interfere with the optimal performance of the EAS system. Further, some unscrupulous individuals utilize EAS marker shielding, e.g., metal foil, with the intent of shoplifting merchandise without detection from any EAS system. The metal can shield tagged merchandise from the EAS detection system.
Current EAS systems implementing metal shielding detection mechanisms may sometimes be fooled by various cart configurations and overpowered by the response of a large mass of metal. Some systems attempt to overcome this problem by lowering the gain of the system, which limits the sensitivity and reduces the detection capability for small items, such as the metal shielding they are trying to detect.
Other conventional systems may include a “shopping cart inhibit” feature in the EAS system/metal detection configuration. By monitoring the overall mass of the metal response signal, a threshold can be implemented indicating an inhibit situation so that the system will not falsely generate an alarm. However, even with this solution implemented, some store merchandise will continue to fool the system and result in a false alarm or missed detection. For example, detection of large metal shielding positioned close to the pedestals is reduced because these shields produce readings which exceed the thresholds.
Therefore, what is needed is a system and method for independently detecting the presence of a cart or stroller within an EAS interrogation zone, thereby allowing increased sensitivity of an EAS system with metal shield detection capabilities.